This invention relates to an improvement in compressors for use in car coolers, etc.
A gas compressor adapted to be used in air cooling for passenger cars, etc. is usually juxtaposed with an engine of the motor vehicle to be driven by a crank shaft pulley of the engine through a V-belt, and a solenoid clutch provided on the compressor side serves to make connection with or disconnection from the driving side (i.e., the engine).
Accordingly, the refrigerating capacity of such a gas compressor is enhanced substantially in proportion to the engine speed. Long time driving of the engine causes over-refrigeration of the car interior because the gas compressor is driven also at high speeds. In addition, power consumption by the compressor is increased and the temperature of the discharged gas is raised up correspondingly. This disadvantageous tendency is particularly remarkable in a rotary type gas compressor because compressors of this type have no intake valve and have a lesser amount of residual compressed gas in the working chambers of the compressor thereby resulting in an increased volumetric efficiency during high-speed driving.
To prevent such excessive air cooling, there has been proposed a technique, for example, in which the solenoid clutch is engaged or disengaged in response to an output from a temperature sensor provided on an evaporator or on some other part so as to operate the gas compressor under ON/OFF control.
However, this technique has the drawback that the solenoid clutch is subject to substantial wear because of its repeated engagement and disengagement and load fluctuations of the engine are enlarged.
There has been also proposed a technique in which a throttle valve is provided in a flow passage in communication with an intake port to narrow the opening area during high-speed rotation so that the intake loss is enlarged to restrict an increase in the compression capability. But this method is disadvantageous since it results in an increased engine load.